Our best friends have hosted 3 international students, each for a full academic year. I know, not the same as hosting them myself, but we are very close as families, have dinner together at least once a week, and are often in and out of each other's houses. They have one son and one daughter, both of whom were in high school when they were hosting students of the same ages. Here is their experience:
First off, the group they worked with interviews families to decide if they are a good fit. Our friends were able to read profiles, and the agency had to agree to the match. Students aren't allowed to drive while in the US, have to have their own medical insurance, and have to use the medical/dental practices approved by the agency. This is all very well-regulated so hopefully there are no "horror stories" and both student and host family have a wonderful experience.
Student #1 was a boy from Saudi Arabia, 16 year old high school junior. He was the youngest of 6 children and the only boy in the family. They all liked each other, but he came from a wealthy family and really was a little prince. Very picky eater, self-indulgent, didn't understand why he had to fit in with everyone else, follow family rules, etc. My friends scaled back a few expectations and the student learned that he was a part of a family and had to follow rules. It was a hard year for everyone, although they all learned to like each other well enough.
Second student was a boy from Thailand. He'd been placed in one family and it wasn't working out, he was very homesick, etc. Although my friends hadn't planned on taking another kid, they agreed to bail out the program temporarily, until another family could be screened. Well, that never happened, because this student and my friends clicked so well. He was an only son with 2 sisters and a large extended family who all lived in the same neighborhood. He fit into family routine, loved to visit and laugh with us at dinner, would sit around the kitchen and talk while people were cooking, cooked dinner for the family once a week, etc. It was a wonderful experience for all, and they still hear from him.
Their 3rd student was a girl from Denmark. It was love at first sight for everyone. It's amazing how she fit into the family, like another daughter. There isn't too much more to say. They are still in close contact with this student, and now that she's married an American guy they see her/them at Thanksgiving, Christmas, and during many school holidays (she's a teacher). Our friends went to Denmark when this girl got married, and the dad of this family walked her down the aisle as her own dad passed away a few years ago.
SO there's one family's experience with 3 different students. All were learning experiences, all went well in most ways... Good luck with whatever you decide to do!